Manufacturing method of colored polylactic acid resin

Abstract

Disclosed is a technique of providing color to a polylactic acid resin which is promising as a plant-derived material for automotive interior/exterior parts. When a polylactic acid material is used as a covering fiber material of an automotive interior part, coloring is necessary for harmonization with other parts in the car. According to the disclosed technique, color is provided to a polylactic acid resin using a combination of a catalyst and an initiator when it is polymerized from lactide. The disclosed method is time-saving and economical since a colored resin can be polymerized and thus the complicated process of dyeing a white resin using a disperse dye and washing and drying the same can be avoided.

1 . A method for preparing a colored polylactic acid, comprising the steps of:
 (a) synthesizing an aluminum catalyst and one or more ligands in a solvent to form an aluminum catalyst complex; and   (b) polymerizing polylactic acid by adding lactide monomers and a color determining selective initiator to the solvent and catalyst complex of step (a).   
     
     
         2 . The method according to  claim 1 , wherein the solvent is an organic solvent. 
     
     
         3 . The method according to  claim 2 , wherein the organic solvent is toluene, benzene, pentane, cyclopentane, hexane, cyclohexane, chloroform, diethyl ether or 1,4-dioxane. 
     
     
         4 . The method according to  claim 1 , wherein the aluminum catalyst complex is prepared by mixing 1 equivalent of trimethylaluminum with 2 equivalents of C 5 H 4 N(CO)NHC 6 H 3 (NO 2 ) 2 . 
     
     
         5 . The method according to  claim 1 , wherein the color determining selective initiator comprises an alcohol functional group. 
     
     
         6 . The method according to  claim 5 , wherein the selective initiator is HOCH 2 (C 6 H 4 )N═N(C 6 H 4 )NH 2 , 2-[N-ethyl-3-methyl-4-[(5-nitro-1,3-thiazol-2-yl)diazenyl]anilino]ethanol, 2-[4-(2-chloro-4-nitrophenyl)diazenyl-N-ethylanilino]ethanol, 1-pyrenebutanol or a mixture thereof. 
     
     
         7 . The method according to  claim 1 , wherein the aluminum catalyst complex and the selective initiator are independently added in an amount of 0.5-0.7 part by weight based on 100 parts by weight of the lactide monomers. 
     
     
         8 . The method according to  claim 1 , wherein the polylactic acid polymerization is performed at 160-250° C. for 0.5-3 hours. 
     
     
         9 . A polylactic acid resin having a molecular weight of 50,000-200,000, which is prepared by the method according to  claim 1 .